We propose to extend our research on IR Natural and Magnetic Circular Dichroism in the areas of Vibrational Circular Dichroism and Metalloproteins. We have recently observed vibrational CD in the C-H and O-H stretch regions of CF3CH(OH)C6H5 with high signal-to-noise ratio, significantly extending and improving on the previously reported spectrum of Holzwarth et al. We propose to extend this work and to study a large range of organic and biological materials, both small and large. In view of the intrinsically small strength of vibrational CD we propose to make significant instrumental improvements wherever possible. In particular, the addition of laser light sources will be made as practicable; initially a CO2 laser will be added permitting measurements over approximately 200/cm with an effective resolution of approximately 1-2/cm. Molecules for study will be chosen with a view to relevant instrumental considerations and the potential interest of data. From a basic standpoint, the ability of theory to interpret and predict experimental observations will be studied. Practical applications of vibrational CD will also be explored; these may be most obviously expected in the areas of absolute configuration and conformational stereochemistry. In the area of metalloproteins we will study the CD and MCD of near IR electronic transitions in both metalloproteins and synthetic model systems. A major initial effort will be the development of MCD as a tool in the study of heme proteins. By constructing a theory of heme electronic states which satisfactorily handles the MCD of well-defined hemes, we will generate a tool for the characterization of new heme systems and for the elucidation of their chemical, geometrical and electronic structure. This can be applied to problems relating to the function of heme proteins and to the evaluation of the quality of modelling achieved by synthetic systems. Studies of proteins containing other metal ions and of their model analogues will also be pursued.